Speech amplifying and reproducing system



April 22, 1930. LE ROY MARK SPEECH AMPLIFYJING AND REPRODUCING SYSTEM 2 Sheets-Sheet 1 Filed July 16, 1927 INVENTOR l6 BY ATTORN%Y AprH 22, 1930. LE ROY MARK 1,755,484

SPEECH AMPLIFYING AND REPRODUCING SYSTEM Filed July 16, 1927 2 Sheets-Sheet 2 IN VEN TOR.

-Ze 15 0 /1/02" j BY 5 diff; ATTORNEY 7 Patented Apr. 22, 1930 UNITED STATES LE BOY IMLARIK, OF WASHINGTON, DISTRICT OF COLUMBIA.

SPEECH AMPLIFYING AND BEPRODUCING' SYSTEM IAppliatiou filed July 16,

My invention relates broadly to public ad dress systems and more particularly to a construction of microphone and amplification circuit arrangement'for use in public address systems.

One of the objects of my invention isto provide a construction of-microphonic pickup andcontrol system for public address sys-- tems in which a high degree of sensitivity 110 is obtained for effecting reproduction of sound at relatively large volume.

Another object of my invention is to provide a construction of microphonic pick-up apparatus which is compact in size and yet 1 which may be arranged in circuit with an electron tube amplification. system for controlling the operation of the electron tube amplification system for reproduction of sound at-relativel large volume. Still another 0 ject of my invention is to provide a construction of microphonic pickup system in which aplurality of independent microphones may be arranged in compact manner for simultaneously controlling the input circuit of an electron tube amplification system. I

A still further object of my invention is to provide a construction of microphonic pick-up apparatus for public address systems in which a plurality of independent microphones are arranged in staggered relation ship for actuation by sound waves and the control of an amplification and reproducing system thereby. I 4

My invention will be more fully understood from the specification hereinafter following by reference to the accompanying drawings in which: Figure 1 is a front elevation of the microphonic pick-up apparatus of my invention; Fig. 2 is a cross-sectional view taken through v the microphoniciappara tus on line 22 of Fig. 1; Fig. 3 is a cross-sectional view taken through the'pick-up apparatus on line 3- 3 of Fig. 1; Fig. 4 is a wiring diagram showing the arrangement of the multiple control V r of microphone system in the microphonic pick-up apparatus of my invention; Figs. 5 and 6 show front and side views of a modified construction of microphone apparatus 1927. Serial No. 206,341.

embodying the principles of my invention; Fig. 7 is a vertical cross-sectional view through the microphone apparatus of Figs. 5 and 6; Fig. 8 is a cross-sectional view taken on line 88 of Fig. 7; and Figs. 9 and 10 are views of the microphone support employed in the modified form of the invention illustrated in Figs. 5-8, inclusive.

Referring to the drawings in more detail, reference character 1 designates the base of m the microphonic pick-up apparatus of my invention on which there is mounted a housing consisting of a front panel 2 and a rear panel 3 with end panels 4 and 5 connected thereto.

A. top closure 6 is provided, and between the (35 upper surface of the supporting base 1 and the lower surface of. the top closure 6 a plurality of independent microphones are mounted in vertical planes in the arrangement illustrated. I have designated the mi- N c'rophones at 7, 8, 9, 10 and 11, each mounted in a vertical plane as illustrated, which planes are parallel to each other but oflset one with respect to the other, the center lines of the individual microphones 8and 10 passing between the spaces which separate the microphones 7 9 and 11. The under surface of the top closure 6 is cut away as designated at 12 forming pockets which receive the upper part of the individual'microphones. The upper 0 portion of the base 1 is cut away to providepockets designated at 14 to receive the lower portions of the individual microphones. The pockets 12 and 14 are vertically aligned with each other thereby enabling the microphones to be rigidly mounted in position within the cabinet housing. The microphones\are arranged in staggered relationship, the aper-- tures of each microphone facing the front of the cabinet structure with the sides of the microphones overlapping. In this way, a large number of independentmicrophones may be positioned within a relatively small space for controlling the amplification system. The front panel 2 is apertured'as represented at 15 and over the aperture an ornamental grille 16 is placed. v

The circuit arrangement for the microphone pick-up system of my invention is il lustrated in Fig. 4t wherein the independent we microphones 7,8, 9, and 11 are each connected in circuit with a common source. 17 and with independent primary windings 18. 19, 20, 21 and 22 of the iron core transformer 23. Each microphone has an independent rimary winding, the potential across which is independently varied by the operationiof its associated microphone. The transformer- 23 has a secondary winding 24, the secondary winding being connected across the input circuit of electron tube 25 and arranged to function as an audio frequency amplifier. A coupling system 26 is provided between the output circuit of the amplifying tube 25 and the input circuit of the amplifying tube 27. The output circuit of the electron tube 27 includes the loud speaker 28. A suitable choke '29 and condenser 30 may be arranged in circuit with the loud speaker 28 fo r improving the tone quality of the reproduced sound. The conductors from each of the independent microphones are shown leading to the local source and to the several microphone circuits through twisted cables which enable the microphone'to be located at a distant po'intremote from the amplifying system, thereby facilitating installation of the apparatus in a public address system. V

The alignment of the several microphones in staggered'relationship increases the number of units which may be provided within a limited area.

The modified form of microphone apparatus constructed in accordance with my invention shown in Figs. 5-10 comprise a supporting stand 42 carrying a circular band member 31 to which is secured the'front and rear closure members 32 and 33 by means of screw members 50. The side closures 32 and 33 are each provided with suitable apertures 48, which apertures may be covered by a suitable ornamental grille. The grille which shows through the central aperture 51 and the apertures 48 is merely forthe purpose of ornamentation as the inside wall is substantially closed by means of a felt lining 49. It serves as a sound damping chamber extending upwardly around the inside of the circular frame 31 and along the rear of the several microphones so that sound waves incident upon the several microphones strike the rear felt wall 49 and do not pass through the rear apertures 48 and 51. I provide a frame or casting 34 resiliently' supported interiorly of the casing-31 by means of spring members 46 secured to lug members 47 which extend integrally from the casing 31. The spring members 46 extend substantially at right angles to each other between screw devices 43 on casting 34 and lug members 47 on casing 31. The casting 34 is provided with screw devices 43 symmetrically positioned about the casting, so that several microphones may be positioned in spacial relatio'n'andin a position for receiving sound vibrations directed thereagainst. The casting 34 includes two pairs of symmetrically arranged casing'portions, each forming sockets disposed in the same plane into which microphones can be secured. The casting 34 is also provided with a socket portion 35 in. a plane offset from the four socket members for receiving an independent microphone in a plane offset from-the plane of the microphones in the aforementioned sockets.

I have illustrated four microphones 36, 37 38 and 39 disposed in one plane and an additional microphone 40 in staggered relationship with respect to the aforementioned four microphones by reason ofthe relation of the sockets whichcarry the several microphones. Screw -devices 41 are provided for securing each of the microphones in position. In addition to this, strapmembers 44 are secured beneath the heads of the screw members 43 for maintaining the microphones. in position within the sockets. The strap members 43 extend over the flanges on the microphones. In order to cushion the microphones within the casing I provide cushion members 45 adjacent each of the microphone sockets. so that in the natural course of vibration of the microphones there is no danger of sudden shocks and jars whichmight injure the sensitive microphone devices. Connections from the several microphones lead out from the cable 43 to the control circuits of the amplifier system. It will be observed that the staggered relationship in the modified form is similar to that in the form of the invention and described in Figs. 1 to 4 in addition to the fact that more compact assembly of the apparatus is secured.

While I have described my invention in certain of its preferred embodiments, I desire it to be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. Microphonic pick-up apparatus comprising a frame,a casing within said frame, a plurality of sockets disposed in said casing in planes laterally off set one from the other, said sockets being arranged to receive and enclose independent microphones, at leastone of said microphones being ofl set fromla source ofsound by a distance greater than the others of said microphones and spring members grouped in'pairs with the pairs of each oup extending substantially at right ang es to each other between diametrically opposite positions on said casing and positions on the interior of said frame.

2. Microphonic pick-up apparatus com prising a'frame, a carrier, pairs of symmetrically arranged sockets in said carrier disposed in a' single plane, a separate socket centrally positioned in said carrier in a plane ofi. set

from the plane of said aforementioned sockets, independent microphones disposed in each of said sockets, one of said micro hones being located at a greater distance rom a source of sound than the others of said microphones and means disposed-between the sides of said carrier and said frame for centering said carrier withinsaid frame.

3. Microphonic pick-up apparatus comprising a frame, a resiliently supported carrier, dis osed within said frame, sockets symmetrica 1y arranged in one side of said carrier in the same plane. a socket centrally disposed on the other side of saidcarrier in a plane ofl set from the plane of said first mentloned sockets, said sockets being arranged to receive independent microphones, said microphones being disposed in different planes with respect to a source of sound and means extending from the interior of said frame and resiliently engagin the sides of said carrier for damping the vibration thereof.

In testimony whereof I afliii my si at-ure.

LE ROY Milt 

